Simulating Trout Feeding Stations in Instream Flow Models

Abstract

Hydraulic simulation has several variations, but each predicts depth and velocity distributions over an array of discrete, contiguous units of streambed area ('cells') at a series of specified stream discharges. Substrate or cover values are assigned to each cell. The habitat function, HABTAT, uses substrate or cover together with depth and velocity at a specified discharge to calculate a relative habitat value for each cell. Relative habitat value multiplied by surface area of the cell is summed for all cells to yield a weighted usable area (WUA) for each specified discharge. HABTAT uses functions called habitat preference curves or suitability of use criteria to calculate relative habitat value given depths, velocity, and substrate or cover. Habitat preference curves assign weighting or a preference factor ranging from 0 to 1 to each habitat value. A preference factor of 0 for velocity V sub z implies that adult rainbow trout do not inhabit water with velocity V sub z. A preference factor of 1 for velocity V sub y implies that the adult rainbow trout inhabit water with velocity V sub y as much as or more than any other velocity, all else being equal. WUA can be very sensitive to habitat preference curves. (See also W89-01736) (Lantz-PTT)